RECENT CRACKS IN HISTORIC CAPITOL

The Texas State Capitol is a landmark in Austin, Texas. It was originally constructed in 1888 using solid limestone, and there have been many additions and renovations to modernize the structure and adapt it to the needs of the state. Cracks were observed in an original limestone beam over a high pedestrian traffic area at the interface with an addition completed in the early-1990s. Because the limestone is weak in tension and not reinforced, the cracks were concerning for the structural integrity of the beam. In addition, there were some repairs present on the beam that were not documented, so their purpose and extent were not clear. Since the structure is historic, destructive testing was not an option. Engineers from Pivot were retained by Building Diagnostics to perform non-destructive testing (NDT) to provide additional information on the nature of the crack and undocumented repairs. In addition, Building Diagnostics requested an elevation survey to estimate the applied loads to the beam and compare to existing drawings.

Pivot performed detailed visual observations and documented conditions at the time, including representative crack widths. With a better understanding of the visible conditions, surface penetrating radar (SPR) and impact-echo were used to gather information within the beam. The cracked beam areas were the focus of the investigation, but beam areas without cracks were also tested for comparison and calibration purposes. The NDT characterized the extent and definition of the cracking below the surface and covered areas, and the visual observations provided a reference point for future comparison. The elevation survey determined the beams were supporting a few feet of material to the underside of the entry floor above, which may have been increased as a result of the undocumented remodel. The information provided by engineers from Pivot was essential to decision-making by Building Diagnostics and Texas State Preservation Board, who maintains the Texas Capitol.

PROJECT SERVICES:

Structural Assessment (Visual)

Nondestructive Testing

Impact-Echo

Surface Penetrating Radar

Elevation Survey